Glass containing lead refers to glass containing glass-formers like SiO2 and high level of PbO, which is often used for manufacturing products as optical glass, electric vacuum glass, low-temperature sealing glass, anti-radiation glass, glass beads with high refractive index and art container glass, etc.
As an important product of glass containing lead, cathode ray tube (CRT) is widely used in televisions, computer monitors, oscilloscope and other electronic equipments. Glass of CRT monitor contains a lot of PbO as well as a variety of harmful chemical ingredients, such as: 53.05% SiO2, 18.27% PbO, 3.47% Al2O3, 2.35% CaO, 1.9% BaO and 0.97% MgO (by mass fraction). Especially the glass of the funnel contains lead up to 20% to 40%. If discarded directly, it may not only cause a waste of lead resources, but also produce huge pollution to the surrounding environment, even serious harm to human health.
Because CRT displays produced in early days have reached or are about to reach the service life, and electronic technology products update at a fast speed, more and more CRT displays are (will be) obsolete and become e-waste. According to a statistics in 2008, the number of obsolete televisions and computers in China was over 500 million each year, and increased at the rate of 25 to 30% year by year. Thus, how to treat waste glass containing lead has become a hot issue of concern.
In recent years, it has been reported that sintered glass ceramics can be obtained after mixing glass containing lead and some industrial wastes followed by grinding into powders and sintering, but in this way, it is just to transfer metal lead in the glass from one product to another product, the problem of hazard of heavy metals has not been solved.
In 2008, Wu Guoqing, et al, reported a research entitled “study on technique for recycling and treating displays containing CRT” from the perspective of material classification, harmless disposal of material, material separation and recycle. That same year, Yin Fengfu, et al, at the Haier Group's technology research and development center reported a research entitled “environmental processing technology of waste displays”, as well as its partner Qingdao Xintiandi developed CRT comprehensive utilization technology, built relevant disposal and recycling factories, but their technical core is limited to CRT dismantling and classification, and does not involve in industrial production methods of extracting lead from CRT for reuse.
A Chinese patent having publication No. CN 101613802A provided a process and corresponding equipments for recycling waste glass containing lead while producing environmental building material, which takes waste glass containing lead as raw material, recycling lead therein by vacuum carbothermic reduction process and preparing foam glass. However, the process has fewer steps so it can only recycle lead and corresponding chemical product at the same time, and the process should be carried out at 1000° C. for several hours which not only requires high demands for equipments but also causes large scale energy consumption and pollution, so it is not suitable for industrial production.